Method of electrochemical hydrodimerization of olefinic compounds

ABSTRACT

A method of electrochemical dimerization of olefinic compounds of the general formula CH2=CHX, wherein X is a nitrile, ester, amide, aldehyde or carboxy group, according to which a mixture consisting of an aqueous solution of acid salts of an alkali metal and polybasic acid and olefine is subjected to electrolysis in an electrolytic cell provided with an oxide anode and with a cathode made of graphite impregnated with ion-exchange polymers that are insoluble in the reaction mixture and contain a tetraalkylammonium group or a substituted tetraalkylammonium group, the electrolysis being effected at a cathode current density of 300-1,600 A/m2, a pH of 7-9, and at a temperature of 17*-25* C.

United States Patent Tomilov et al.

[451 May 9,1972

[54] METHOD OF ELECTROCHEMICAL HYDRODIMERIZATION OF OLEFINIC COMPOUNDS [72] Inventors: Andrei Petrovich Tomilov, 5 Parkovaya ulitsa 56, korpus 6, kv. 59; Vladimir Alexeevich Klimov, Butyrsky val, 26, kv. 50; Semen Lvovich Varshavsky, ulitsa Pavla Andreeva, 28, kv. 282, all of Moscow, U.S.S.R.

221 Filed: Sept. 29, 1969 21 Appl.No.: 862,010

[51] Int. Cl. ..C07b 29/06, C07c 121/26 {58] Field of Search ..204/73 R, 73 A [56] References Cited UNITED STATES PATENTS 3,385,780 5/1968 Feng ..204/291X 3,427,234 2/1969 Guthke ..204/73A 3,477,923 11/1969 Becketal. ..204/73A FOREIGN PATENTS OR APPLICATIONS 813,877 5/1969 Canada ..204/73A 1,548,304 10/1968 France ..204/73A Primary Examiner-F. C. Edmundson Attorney-Waters, Roditi, Schwartz & Nissen [57] ABSTRACT A method of electrochemical dimerization of olefinic compounds of the general formula CH CHX, wherein X is a nitrile, ester, amide, aldehyde or carboxy group, according to which a mixture consisting of an aqueous solution of acid salts of an alkali metal and polybasic acid and olefine is subjected to electrolysis in an electrolytic cell provided with an oxide anode and with a cathode made of graphite impregnated with ion-exchange polymers that are insoluble in the reaction mixture and contain a tetraalkylammonium group or a substituted tetraalkylammonium group, the electrolysis being efiected at a cathode current density of 3001,600 A/m", a pH of 7-9, and at a temperature of 1725 C.

8 Claims, N0 Drawings METHOD OF ELECTROCHEMICAL HYDRODIMERIZATION OF .OLEFINIC COMPOUNDS The present invention relates to methods of hydrodimerization of olefinic compounds which are used as products for producing polyamides serving as a basis for obtaining synthetic fibers or plastics, and also as plasticizers in various branches of polymer chemistry.

Known in the art are methods of electrochemical hydrodimerization of olefinic compounds with the general formula Cl-l CHX where X is a nitrile, ester, amide, aldehyde, or carboxy group, for example, a method of producing adiponitrile by electrochemical hydrodimerization of acrylonitrile, according to which a mixture consisting of an aqueous solution of acid salts of an alkali metal and polybasic acid and acrylonitrile is electrolyzed, with adding surface-active agents to said mixture, such as quaternary ammonium salts, substituted triazine bases, and the like.

The process is carried out in a diaphragmless cell with the use of an oxide anode which is essentially an alloy of iron oxides and silicon and titanium oxides taken in the following proportions (wt.%): silicon oxides, to and titanium oxides, 0 to 10. The electrolysis is effected at a cathode current density of 400-1600 Alm a temperature of l8-25 C. and a linear velocity of circulation of the reaction mixture in the interelectrode space of 0.3 m/sec. After the electrolysis, the organic phase is separated from the reaction mixture, wherefrom the target product is then isolated. The current efficiency is 75-85 percent, and the yield of the target product is 85-92 wt.% (see Luxemburg Pat. No. 51,624). Y

The known methods are disadvantageous due to the use of quaternary ammonium base salts which are highly soluble in the organic phase of the emulsion, which necessitates their regeneration, whereby the process becomes more complicated and considerable losses of these salts are involved.

Additionally, the use of these salts results in the formation of high-molecular reduction products, this reducing the yield of the target product and impairing its quality.

An object of the present invention is to simplify the technology of the process and improve the quality of the target product.

This object is obtained in the present method of electrochemical dimerization of olefinic compounds with the general formula Cl-l CHX where X is a nitrile, ester, amide, aldehyde or carboxy group, according to which a mixture comprising an aqueous solution of acid salts of an alkali metal and polybasic acid and olefine is electrolyzed in an electrolytic cell with an oxide anode and a graphite cathode at a cathode current density of 300-1 ,600 A/m a pH of 7-9 and a temperature of l7-25 C., according to the invention, the electrolytic cell cathode is made of graphite impregnated with ion-exchange polymers insoluble in the reaction mixture, said polymers containing a tetraalkylammonium group or a substituted tetraalkylammonium group.

The cathode is prepared by impregnating graphite with a solution of monomers, viz, styrene, divinylbenzene, vinylnaphthalene, or acenaphthylene with an initiating agent, by polymerizing said monomers in the pores of graphite at a temperature of 40-80 C., and by subsequent conversion of the obtained polymers to the ion-exchange form. The process of converting the obtained polymers to the ion-exchange form may be efiected in two ways.

According to one possible version the obtained polymers are treated by a mixture of chloromethyl ether and stannic chloride taken in a ratio from :1 to :1 during 40-80 hours, then washed with acetone and water, dried at a temperature of 40-70 C., reacted with triethylamine at a temperature of 60-85 C. during 40-50 hours, and the resulting salt form of the ion-exchanger is treated with a 5-15 percent alkali solution to convert it to the basic form.

According to the second possible version the obtained polymers are treated for 40-50 hours by a 40-60 percent solution of chlorosulphonic acid in dichloroethane, the resulting sulphonyl chlorides are hydrolized with distilled water at a temperature of -80 C. for 20-30 hours, and the obtained H form of the ion-exchanger is treated with 5-15 percent aqueous solution of tetraalkylammonium hydroxide to convert the ion-exchanger to the salt form.

'It is preferable to use benzoylperoxide in an amount of 0.5-1.5 wt.% as a polymerization catalyst.

The cathode may also be prepared by impregnating graphite with a solution of a mixture of two monomers, styrene and divinylbenzene, vinylnaphthalene and divinylbenzene, acenaphthylene and divinylbenzene, or styrene and butadiene, taken in weight ratios of from 50:1 to 1:50, with an initiating agent, by copolymerizing said monomers in the pores of graphite at a temperature of 40-80 C., and bysubsequent conversion of the obtained copolymers to the ion-exchange form.

The conversion of the copolymers obtained to the ionexchange form may likewise be effected in two modified versions.

According to one possible version the obtained copolymers are treated with a mixture of chloromethyl ether and stannic chloride taken in a weight ratio of from 20:1 to 40:] during 40-80 hours, washed with acetone and water, dried at a temperature of 40-70 C., reacted with triethylamine at a temperature of 60--85 C., during 40-50 hours, and the obtained salt form of the ion-exchanger is treated with a 5-15 percent solution of alkali for converting the ion-exchanger to the basic form.

chlorosulphonic acid'in dichloroethane, the resulting sulphonyl chlorides are hydrolized with distilled water at a temperature of 4580 C., for 20-30 hours, and the obtained 1'1 form of the ion-exchanger is treated with 5-15 percent aqueous solution of tetraalkylammonium hydroxide to convert the ion-exchanger to the salt form.

It is preferable to use benzoylperoxide in an amount of 0.5-1.5 wt.% as an agent initiating the copolymerization.

As a mixture of two monomers it is preferable to use a mixture of styrene and divinylbenzene taken in a weight ratio of from 6:1 to 1:10. t

The method of the present invention is effected as follows.

An electrolytic cell is charged with a mixture comprising 60-80 wt.% of 1.5-3 N aqueous solution of acid salts of an alkali metal and 20-40 wt.% of olefin. The mixture is emulsified with a centrifugal pump and continuously passed into the interelectrode space with a linear velocity of 0. l-0.3 m/sec. The electrolysis is carried out at a cathode current density of 300-1 ,600 Alm a pH of 7-9 and a temperature of 17-25 C. The cathode used in the process of electrolysis is a rod made of graphite impregnated with ion-exchange polymers insoluble in the reaction mixture, which contain a tetraalkylammonium group or a substituted tetraalkylammonium group. The cathode is preparedby impregnating graphite with a solution of a monomer or of a mixture of monomers with a polymerization-initiating agent, after which the monomers are polymerized in the pores of graphite at a temperature of 40-180 C. For converting the obtained polymers and copolymers to the ion-exchange form, two versions of their treatment may be employed.

The first version consists in that graphite with the polymers and copolymers formed in the pores thereof is treated with-a mixture of chloromethyl ether and stannic chloride taken in a weight ratio of from 20:1 to 40:1, preferably 30:1, during 40-80 hours, washed with acetone and water, dried at a temperature of 40-70 C., whereupon the graphite electrode is treated with triethylamine at a temperature of 60-85 C. during 40-50 hours.

The resulting cathode is impregnated with an ion-exchanger in the salt form which is then converted to the basic form by treating the ion-exchanger with a 5-15 percent solution of alkali.

According to the second version, graphite with the polymers and copolymers formed in its pores is treated with a 40-60 percent solution of chlorosulphonic acid in dichloroethane at room temperatures during 40-50 hours.

According to the second version the obtained copolymers are treated for 40-50 hours with a 40-60 percent solution of v The resulting sulphonyl chlorides are hydrolized with distilled water at a temperature of '45 80 C. The hydrolysis is completed after 20-30 hours. The obtained cathode is impregnated with a cation-exchange resin in the l-i form which is then converted to the salt form by treating with a -15 percent solution of tetraalkylammonium hydroxide.

In the process of hydrodimerization, use may also be made of a cathode, impregnated with ion-exchange polymers containing phosphate and carboxy groups after having been converted to the salt form.

I After electrolysis an organic phase is separated from the reaction mixture, wherefrom the target produced is isolated by rectification. The yield of the target product is 70-95 per-. cent as calculated for the current efficiency, and 90-95 wt.% of the stock used.

The advantages of the method proposed herein reside in that the use of a graphite cathode impregnated with ionexchange polymers makes it possible to dispense with the employment of quaternary ammonium salts, whereby the process becomes simplified through the exclusion of the regeneration stage of quaternary ammonium salts from the products of hydrolysis; the amount of by-products being reduced and the quality of the target improved.

The invention may best be understood by reference to the following examples of carrying out the present method of electrochemical hydrodimerization of olefinic compounds.

EXAMPLE 1 v .A diaphragmless electrolytic cell provided with an oxide anode and a cathode which is a rod made of graphite impregnat ed with an anion-exchange polymer in a basic form based on styrene, is charged with a mixture composed of 260 ml. of 2N aqueous solution of potassium hydrogen phosphate and 140 ml. of acrylonitrile. The mixture is emulsified with a centrifugal pump and continuously passed between the cathode and anode with a linear velocity of 0.2 m/sec. The electrolysis is carried out at a cathode current density of 350 A/m, at a temperature of 18 C. and a pH 8. With a current intensity of 5 A the electrolysis lasts for 4 hours.

The electrolysis being completed, an organic layer is separated, and the target product is isolated therefrom. 32.84 g. of adiponitrile are obtained,which corresponds to a current efficiency of 82.0 percent; the yield as calculated for the acrylonitrile used is 91.2 wt. I

Said graphite cathode is prepared in the following manner. A rod of porous graphite is placed into a thick-walled vessel which is provided with a dropping funnel and a gas-escape tube and kept there in a vacuum of 2-5 millimeter of mercury for 1 hour at a temperature of 80 C. After cooling, the vessel is rapidly filled with a mixture comprising 99 parts by weight of styrene and 1 part by weight of benzoyl peroxide, the pressure being gradually raised to the atmospheric. Then the contents of the vessel are heated on a water bath up to 5060 C. and kept till the polymerization is completed during 24 hours.

The impregnated graphite rod is immersed into a mixture of chloromethyl ether and stannic chloride taken in a weight ratio of 30:1. After keeping the rod for 2 days at the boiling point of the ether, the rod is washed'with acetone and then with a sufficient amount of water, whereupon the rod is dried at a temperature of 60-70 C. and treated with an excess of triethylamine at a temperature of 70 C. during 48 hours. The

cathode thus obtained is impregnated with an anion-exchange resin inthe salt form, which is converted to the basic form by a two-fold treatment with a percent aqueous solution of potassium hydrochloride during 20 hours.

EXAMPLE 2 The electrolysis is carried out under conditions similar to those described in Example 1. The initial oleflnic compound used is acrylonitrile. A cathode is employed, which is a graphite rod impregnated with an anion-exchange polymer in the basic form, produced by copolymerization of styrene and divinylbenzene taken in a ratio of 6: l. The cathode is prepared as in Example 1. After electrolysis 34.8 g. of adiponitrile are obtained, this corresponding to the current efficiency of 87 percent. The yield of the target product, as calculated for the acrylonitrile used, is 92.2 wt.

EXAMPLE 3 The electrolysis is carried out under conditions similar to those described in Example 1. The initial olefinic compound used is acrylonitrile. A cathode is employed, which is a graphite rod impregnated with an anion-exchange polymer in the basic form, produced by copolymerizing styrene and divinylbenzene taken in a ratio of 18:1. The cathode is prepared as described in Example 1. 31.55 g. of adiponitrile are obtained, which figure corresponds to the current efficiency of 78.6 percent. The yield of the target product, as calculated for the acrylonitrile used, is 90.2 wt.%. Y

" EXAMPLE 4 The electrolysis is carried out under the same conditions as in Example 1. The initial olefinic compound used is acrylonitrileuA cathode is employed, which is a graphite rod impregnated with an anion-exchange polymer in the basic form, produced by copolymerization of vinylnaphthalene and. divinylbenzene taken in a ratio of 15:1. The cathode is' prepared as described in Example 1. 32.3 g. of adiponitrile are obtained, this quantity corresponding to the current efi'iciency of 80.7 percent. The yield of the target product, as calculated for the acrylonitrile used, is 91.3 wt.%.

EXAMPLE 5 y EXAMPLE 6 The electrolysis is effected under conditions similar to those described in Example 1. The initial olefinic compound used is methylacrylate. A cathode is employed, which is a graphite rod impregnated with a cation-exchange polymer produced by copolymerization of styrene and divinylbenzene taken in a ratio of 8:1. 30.1 g. of dimethyladipate are obtained, which corresponds to the current efficiency of percent.

Said cathode is prepared in the following manner. A graphite rod is impregnated with a mixture of monomers, styrene and divinylbenzene, and copolymerization is effected as described in Example 1. The impregnated rod is kept in a 50 percent solution of chlorosulphonic acid in dichloroethane for 40 hours at a room temperature. The resulting sulphonyl chlorides are hydrolized with distilled water at a temperature of 40-50 C.

. The hydrolysis is completed after 20-30 hours. On completion of the hydrolysis the graphite rod is immersed for 1 hour into a 10 percent aqueous solution of tetraethylammonium hydroxide for converting the l-F-form of the cation-exchange resin to the salt form.

EXAMPLE 7 tion-exchange polymer based on styrene and butadiene, taken I in a ratio of 16:1. The cathode is prepared by the procedure similar to that set forth in Example 1. 55.0 g. of adiponitrile are obtained, which corresponds to the current efficiency of 91.6 percent. The yield of adiponitrile, as calculated for the acrylonitrile used, is 92.2 wt.%.

EXAMPLE 8.

tion-exchange polymer based on styrene and divinylbenzene taken in a ratio of 14:1. The cathode is prepared by the same procedure as described in Example 6. 55.9 g. of adiponitrile are obtained, which corresponds to a current efficiency of 93.2 percent. The yield of adiponitrile, as calculated for the acrylonitrile used, is 94.2 wt.%.

What is claimed is:

l. A method of electrochemical hydrodimerization of olefinic compounds represented by the general formula CH CHX, wherein X is selected from the group consisting of nitrile, ester, amide, aldehyde and carboxyl, comprising subjecting a mixture consisting of an aqueous solution of acid a1- kali metal salts of polybasic acids and the olefin to electrolysis in an electrolytic cell having an anode and a cathode, said cathode being graphite having formed in the pores thereof an ion-exchange polymer which is insoluble in the reaction mixture and contains a group selected from tetraalkylammonium and substituted tetraalkylammonium, and effecting the electrolysis at a cathodic current density of 300 to 1,600 A/m and atapH of7to9.

2. A method as claimed in claim 1 wherein said ionexchange polymer is incorporated into the cathode by impregnating graphite with a solution of a monomer selected from the group consisting of styrene, divinylbenzene, vinylnaphthalene and acenaphthylene in the presence of a polymerization initiator, followed by polymerizing said monomer at an elevated temperature and converting the resulting polymers to an ion-exchange form.

3. A method as claimed in claim 2 wherein the polymer conversion to ion-exchange form is effected by treating the polymer with a mixture of chloromethyl ether and stannic chloride taken in a weight ratio of from 20:] to 40:1 for a period of 40 to hours, following by washing, drying at a temperature of from 40 to 70 C., treating with triethylamine at a temperature of from 60 to C. and thereafter treating with an alkaline solution.

4. A method as claimed in claim 2 wherein the polymer conversion to ion-exchange form is effected by treating the polymer with a 40-60 percent solution of chlorosulfonic acid and dichloroethane, followed by hydrolyzing the resulting chlorosulfonate with water and treating with a 5-15 percent solution of tetraalkylammonium hydroxide.

5. A method as claimed in claim 1 wherein the incorporating of said ion-exchange polymer into the pores in the graphite is effected by impregnating the graphite with a solution of a mixture of two monomers selected from the group consisting of styrene, divinylbenzene, vinylnaphthalene, acenaphthylene and butadiene, said two monomers being taken in a weight ratio of from 50:1 to 1:50 and said solution containing a copolymerization initiator, followed by copolymerizing said two monomers at elevated temperature and converting the resulting copolymers to an ion-exchange form.

6. A method as claimed in claim 5 wherein said copolymers are converted to ion-exchange form by treatment with a mixture of chloromethyl ether and stannic chloride taken in a weight ratio of from 20:1 to 40:1 for a period of from 40 to 60 hours, followed by washing the thus-treated copolymer, drying at a temperature of from 40 to 70, treating with triethylamine at a temperature of from 60 to 85 C., and thereafter treating with an alkaline solution.

7. A method as claimed in claim 5 wherein said copolymers are converted to ion-exchange form by treatment with a solutron of chlorosulfonlc acid in drchloroethane, followed by hydrolyzing the resultant chlorosulfonate with water and treating with a 5l5 percent solution of tetraalkylammonium hydroxide.

8. A method as claimed in claim 5 wherein the mixture of two monomers comprises styrene and divinylbenzene taken in a weight ratio of from 6:1 to 1:10. 

2. A method as claimed in claim 1 wherein said ion-exchange polymer is incorporated into the cathode by impregnating graphite with a solution of a monomer selected from the group consisting of styrene, divinylbenzene, vinylnaphthalene and acenaphthylene in the presence of a polymerization initiator, followed by polymerizing said monomer at an elevated temperature and converting the resulting polymers to an ion-exchange form.
 3. A method as claimed in claim 2 wherein the polymer conversion to ion-exchange form is effected by treating the polymer with a mixture of chloromethyl ether and stannic chloride taken in a weight ratio of from 20:1 to 40:1 for a period of 40 to 80 hours, following by washing, drying at a temperature of from 40* to 70* C., treating with triethylamine at a temperature of from 60* to 85* C. and thereafter treating with an alkaline solution.
 4. A method as claimed in claim 2 wherein the polymer conversion to ion-exchange form is effected by treating the polymer with a 40-60 percent solution of chlorosulfonic acid and dichloroethane, followed by hydrolyzing the resulting chlorosulfonate with water and treating with a 5-15 percent solution of tetraalkylammonium hydroxide.
 5. A method as claimed in claim 1 wherein the incorporating of said ion-exchange polymer into the pores in the graphite is effected by impregnating the graphite with a solution of a mixture of two monomers selected from the group consisting of styrene, divinylbenzene, vinylnaphthalene, acenaphthylene and butadiene, said two monomers being taken in a weight ratio of from 50:1 to 1:50 and said solution containing a copolymerization initiator, followed by copolymerizing said two monomers at elevated temperature and converting the resulting copolymers to an ion-exchange form.
 6. A method as claimed in claim 5 wherein said copolymers are converted to ion-exchange form by treatment with a mixture of chloromethyl ether and stannic chloride taken in a weight ratio of from 20:1 to 40:1 for a period of from 40 to 60 hours, followed by washing the thus-treated copolymer, drying at a temperature of from 40* to 70*, treating with triethylamine at a temperature of from 60* to 85* C., and thereafter treating with an alkaline solution.
 7. A method as claimed in claim 5 wherein said copolymers are converted to ion-exchange form by treatment with a solution of chlorosulfonic acid in dichloroethane, followed by hydrolyzing the resultant chlorosulfonate with water and treating with a 5-15 percent solution of tetraalkylammonium hydroxide.
 8. A method as claimed in claim 5 wherein the mixture of two monomers comprises styrene and divinylbenzene taken in a weight ratio of from 6:1 to 1:10. 